High efficiency aqueous resole solutions being stable to crystallization and emulsifiable with method of manufacture

ABSTRACT

High efficiency stable aqueous emulsifiable resoles which contain low concentration of free phenol and free formaldehyde and cause substantially less pollution of the atmosphere than prior art resins. The resoles are prepared by a two-stage reaction which controls the molecular weight, water tolerance and the ratio of methylolated 2,2&#39;-, 2,4&#39;- and 4,4&#39;-dihydroxydiphenylmethanes. Stability is promoted by inhibition of the crystallization of bis(4-hydroxy-3,5-dimethylolphenyl) methane.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to stable aqueous solutions of highefficiency emulsifiable phenol-formaldehyde resins and to a process forpreparing the solutions.

2. Description of the Prior Art

A high efficiency single phase aqueous phenol-formaldehyde resin is onewhich has low free phenol and low saligenin (ortho-hydroxy benzylalcohol) and can be aptly described as one in which a high percentage ofthe organic moiety of the aqueous resin is retained when the resin iscured. Free phenol and saligenin volatilize in the curing of the resin,reducing the efficiency and the performance of the resin in variousbonding applications. A high efficiency resin is extremely valuable tothe industry since it results in a greater economic advantage overconventional resins. Even more important is the increase in performanceof the resin in bonding applications. However, one of the unfortunatedrawbacks with a high efficiency single phase aqueousphenol-formaldehyde resin is the instability of the resin which resultsin the formation of a solid or crystal phase. This crystal phase isextremely difficult to dissolve and prevents uniform application of theresin to substrates. Heating the resin to elevated temperatures willhelp to re-dissolve the crystal phase, but unfortunately, such exposureto high temperatures will also advance the resin and affect itsdilutability characteristics thereby affecting its applicationperformance. Filtering out the crystals is uneconomic, reduces theefficiency of the resin and impairs the bonding characteristics.

The prior art (U.S. Pat. No. 3,428,593) teaches stable, high efficiency,single phase, aqueous phenol formaldehyde resins and a process formaking them by reacting phenol and formaldehyde under controlledreaction conditions and a controlled excess of free formaldehyde. Theresin is first prepared by reacting phenol and formaldehyde in certaincritical proportions in the presence of a critical proportion of a basiccatalyst. The reaction is continued until an end point of less than 5weight percent of free phenol is obtained based on the weight of thephenol-formaldehyde resin solids. The free formaldehyde content is thenadjusted to at least 3.0 weight percent by the post addition offormaldehyde thereto. The addition of this formaldehyde keeps the resinstable by driving the equilibrium reaction of formaldehyde and bis(4-hydroxy-3,5-dihydroxymethylphenyl) methane in the direction offorming at least the mono-hemiformal of bis(4-hydroxy-3,5-dihydroxymethylphenyl) methane, to prevent the formationof crystals of bis (4-hydroxy-3,5-dihydroxymethylphenyl) methane. Thismethod of preparing stable high efficiency aqueous phenol formaldehyderesins was a valuable advance in the art. However, the free phenol andfree formaldehyde content of such resins are relatively high and theirpresence in the effluents from the resin applicator's plant cancontribute to atmospheric pollution.

A need therefore exits for high efficiency stable, single phase, aqueousphenol-formaldehyde resins which contain low concentrations of phenoland formaldehyde and thus cause substantially less pollution of theatmosphere than prior art resins. A further need exists for such resinsin emulsifiable form so that they may be used to prepare stable highefficiency phenol-formaldehyde emulsions for impregnation of sheetmembers and cellulosic substrates.

SUMMARY OF THE INVENTION

The above-mentioned need in the art is fulfilled with an aqueoussolution of an emulsifiable resole wherein the solution has a pH lessthan 8.5 and contains less than 2 percent of free phenol, less than 2percent of free formaldehyde and between about 1 and about 12 percent ofan emulsifier based on the weight of the resole and wherein the resolehas a number average molecular weight of less than 300, a watertolerance between about 100 and 800 percent, a combined formaldehyde tophenol molar ratio in the range of 2.0:1 to 2.9:1 and containssufficient methylolated 2,2'- and 2,4'-dihydroxydiphenylmethanes toinhibit crystallization of the resole and wherein the emulsifier isselected to provide a stable emulsion of the resole when water in excessof the water tolerance is added to the solution.

Another aspect of the invention is directed to a process for preparingan aqueous storage stable emulsifiable resole solution which comprises:

a. reacting 1.0 mole phenol with from 0.05 to 0.30 moles formaldehydeunder conditions for formation of novolac resin,

b. adding from 1.75 to 3.5 moles formaldehyde and reacting under basicconditions to produce a resole of molecular weight less than 300, andcontaining less than 2 weight percent free phenol,

c. adjusting the pH of the resole to less than 8.5, and

d. adding between 1 and 12 percent of an emulsifier based on the weightof the resole, selected to provide a stable emulsion of the resole whenwater in excess of the water tolerance is added to the resole solution.

The resoles are manufactured by a carefully controlled two-stage processwhich gives storage stable resins of controlled structure and molecularweight. Because of the high ratio of formaldehyde to phenol (2:1 andgreater) and because the two-stage reaction provides an efficient methodof obtaining a high ratio of combined formaldehyde to phenol, the freephenol content is reduced to a low value of less than 2 weight percentof the resole and concomitantly the free formaldehyde content falls to alow value which can be further reduced by adding a formaldehydescavenger towards the end of the resole reaction.

THE PREFERRED EMBODIMENTS

The aqueous solutions or resoles of the present invention are preparedby a two-stage reaction. The first stage of the reaction is carried outunder novolac forming conditions. Acid conditions are preferred and areobtained with an acid catalyst of pK less than 5 at 25°C., soluble inthe reaction medium. From 0.05 to 0.30 moles of formaldehyde are reactedwith one mole of phenol in this novolac stage. The formaldehyde tophenol ratio is kept low so that dimer formation is favored andformation of higher oligomers is suppressed. The acid catalyst ispreferably a strong acid catalyst of pK less than 2 at 25°C. such ashydrochloric acid, sulphuric acid, oxalic acid, sulfamic acid, benzenesulfonic acid, toluene sulfonic acid or trifluoroacetic acid. It may bea salt of a divalent metal such as zinc chloride, zinc acetate, leadoctoate and similar salts of carboxylic acid which are conventionallyused for the preparation of high ortho novolacs. The concentration ofacid catalyst is in the range of 0.001 to 0.02 mole equivalents per moleof phenol.

The novolac reaction is carried out at temperatures in the range of 60°to 200°C., the particular temperature being readily selected for theappropriate catalyst by the skilled worker in order to obtain novolacmethylene bridged compounds. Normally with strong acid catalyst thereaction is carried out at atmospheric reflux at temperatures in therange of 100° to 120°C.

The acid stage reaction product is believed to be predominantly amixture of the three methylene bridged dimers(2,2'-dihydroxydiphenylmethane, 2,4'-dihydroxydiphenylmethane and4,4'-dihydroxydiphenylmethane). The dimer composition can be varied bymodification of the acid stage catalyst and reaction conditions. Thus,when high ortho directing catalysts such as zinc stearate and othersalts of divalent metals are used the reaction should be carried out atelevated temperatures in order to break orthobenzyl ether groups andform a high concentration of 2,2'-dimer. Strong acids at atmosphericreflux yield a ratio of 2,2'-, 2,4'- and 4,4'- dimers of approximately0.14 to 0.53 to 0.33. Dimer mixtures containing a high proportion of the4,4'- dimer which are less desirable for the purposes of the inventioncan be obtained by reaction of formaldehyde with phenol in the presenceof strong acids at low temperatures in the range of 50° to 60°C.

The methods of carrying out novolac reactions are well known in the art.Thus, the reaction may be effected by reaction of phenol andparaformaldehyde under anhydrous conditions with removal of water ofcondensation by azeotropic distillation or it may be carried out in thepresence of water generated by the reaction or added to the reactionmedium as an aqueous formalin solution containing between 30 and 70percent formaldehyde.

The second stage or resole stage is conducted with a basic catalyst.Typically from 1.75 to 3.5 moles of formaldehyde per mole originalphenol is added for the resole reaction and between 0.05 and 0.30 moleequivalent of base per mole of original phenol in excess of the amountrequired to neutralize any acid which may have been used at the novolacstage. The reaction is carried out at a temperature range of from 40° to80°C. with the preferred range being 50° to 70°C. so that an adequaterate of reaction may be obtained without excessive oligomerization ofthe resole. The reaction is continued until the combined formaldehyde tophenol ratio determined by conventional methods is in the range of 2.0to 2.9.

The resole reaction may also be carried out under anhydrous or hydrousconditions. However, since the resole is subsequently formulated with anemulsifier to form an emulsifiable resole resin which is emulsified bythe addition of water, since pumping and transferring the emulsifiableresole resin requires that the viscosity be low and since low viscosityis conveniently obtained with aqueous solutions of the emulsifiableresole resin, it is generally preferred to carry out the resole reactionwith aqueous formalin solutions containing between 30 and 70 percentformaldehyde. When the reaction is complete, the solids content of theaqueous resole is adjusted to the range of 40 to 70 percent by additionof water or by vacuum stripping to remove water, to provide solutions ofa viscosity in the range which is readily handled in shipping andpumping operations.

The catalyst for the resole stage is a conventional basic catalyst of pKgreater than 9 at 25C. soluble in the reaction medium. Typical basesinclude alkali metal hydroxides such as lithium hydroxide, sodiumhydroxide and potassium hydroxide; alkali metal carbonates such assodium carbonate and potassium carbonate; alkaline earth hydroxides suchas magneisum hydroxide, calcium hydroxide and barium hydroxide; aqueousammonia and amines of molecular weight less than 300. At the end of thereaction the catalyst is neutralized by addition of acid or acid salt toreduce the pH to between 6 and 8.5. for example when the catalyst issodium hydroxide, phosphoric acid is commonly used for neutralization,and sulfuric acid is commonly used to neutralize barium hydroxide.Preferably the pH is adjusted to between 7 and 8.

As is well known in the art, the normal base catalyzed addition reactionof formaldehyde with phenol produces a mixture of 5 mono, di andtri-methylolated phenol monomers which are potential intermediates fordimer formation via condensation. In dimerization of these methylolatedphenols the formation of bis (4-hydroxy-3,5-dimethylolphenyl) methane isfavored and when the ratio of formaldehyde to phenol is high, i.e., whenit is above 2.0, substantial amounts ofbis(4-hydroxy-3,5-dimethylolphenyl methane are formed. Even when theproportion of bis(4-hydroxy-3,5-dimethylolphenyl) methane is relativelylow and the methylolated phenols are in relatively high concentration,the bis(4-hydroxy-3,5-dimethylolphenyl) methane crystallizes out fromconventional resoles when the formaldehyde content is below 3 percentand the pH is adjusted to less than 8.5, particularly at pH in the rangeof 6 to 8 and at low temperatures in range of about 0°-20°C. preferredfor storage. This crystal phase is extremely difficult to redissolve.Elevated temperatures help to redissolved it but unfortunately exposureto high temperatures advances the resin, increasing its molecular weightand decreasing its water tolerance, so that its application performanceis adversely affected. Filtering out the crystals is of little benefitbecause the resulting resin is reduced in efficiency and the bondingcharacteristics are impaired. Moreover, the economics of the processbecome unfavorable and a problem of disposing ofbis(4-hydroxy-3,5-dimethylolphenyl methane is created. By the methods ofthis invention, during the base stage condensation, 2,2'-,2,4'-dihydroxydiphenyl methanes formed during the acid stage, aremethylolated in the same fashion as phenol. Thus the two-stage processintroduces methylolated 2,2'- and 2,4'-dihydroxyphenylmethanes into theresole which, unlike methylolated phenols, unexpectedly suppresscrystallization and precipitation of thebis(4-hydroxy-3,5-dimethylolphenol) methane and allow free formaldehydeto be reduced almost to 0 without impairing the stability of the resoleat normal storage temperatures and pH levels. Moreover, manipulation ofthe acid stage reaction, provides a method of controlling the molecularweight of the resole so that it can be limited to less than 300 andduplication of resoles of molecular weight in the range of 180 to 300with a ratio of combined formaldehyde to phenol in the range of 2.0to2.9 and a reproducible water tolerance is more readily achieved than byprior art processes.

Water tolerance is determined at 25°C. by addition of water to theresole until a slight permanent haze forms. The tolerance is the weightof water expressed as a percent by weight of the resin solids. Thus,where the haze point occurs when 80 parts by weight of water impart hazeto 20 parts by weight of resole resin solids, the tolerance is 400percent. The resoles of the present invention are found to have a watertolerance in the range of 100 to 800 percent.

The amount of formaldehyde reacted with phenol during the acid stage isin the range of 0.05 to 0.30 mole per mole of phenol and is determinedby the amount of methylolated dihydroxydiphenyl methanes needed toimpart adequate storage stability and to control the properties of thefinal resole. The amount required varies with the final combinedformaldehyde to phenol ratio in the resole and depends in part on thepresence of additives and scavengers. Thus, when the combinedformaldehyde to phenol is about 2.0, the amount of formaldehyde reactedin the acid stage can be as low as 0.05 mole per mole of phenol. Whenthe combined formaldehyde to phenol is in the range of 2.5 to 2.9, theamount of formaldehyde reacted in the acid stage is advantageously ashigh as 0.30 mole per mole of phenol.

In general, when the molecular weight of the resole is in the range of180 to 300, the resole contains between 5 and 90 weight percent ofmethylolated dihydroxydiphenyl methanes. In conventional resoles, themethylolated dihydroxydiphenyl methanes comprise almost exclusivelybis(4-hydroxy-3,5-dimethylolphenyl) methane. As a result of thetwo-stage reaction of the present invention, as much as 80 percent ofthe methylolated dihydroxyphenyl methanes may be comprised ofmethylolated 2,2'- and 2,4'-dihydroxydiphenyl methanes. However inpractice, the initial novolac reaction is carried out with proportionsof formaldehyde and phenol which yield final resole compositionscontaining between 5 and 50 weight percent of the methylolateddi-hydroxydiphenyl methanes as methylolated 2,2'- and2,4'-dihydroxydiphenyl methanes to provide stability to the aqueousresole. Because of the high ratio of formaldehyde combined with phenolin the resoles, the dimeric components average between 3 and 4 methylolgroups per molecule.

The two-stage reaction of the formaldehyde and phenol to be carriedalmost to 100 percent completion without stability problems occurring.As a result the phenol content is reduced to below 2 percent based onthe weight of resole and the formaldehyde content is correspondinglyreduced or can be reduced to less than 2 weight percent of the resole byreaction with a formaldehyde scavenger prior to neutralization of thebasic catalyst. Suitable formaldehyde scavengers include sodium sulfite,sodium cyanide and nitrogen containing organic compounds soluble in theresole, of molecular weight less than 300, containing at least 1 NHgroup molecule reactive with formaldehyde. Examples include ammonia,primary and secondary amines, urea, substituted ureas, primary amides,dicyandiamide, guanidine and aminotriazines such as melamine, guanamineand benzo-guanamine. The formaldehyde scavenging reaction is carried outat the end of the resole reaction preferably at a temperature in therange of 20° to 60°C. to minimize oligomerization of the resole. Theamount of scavenger added can vary within very wide limits, up to 0.6mole per mole of phenol in the original reaction mixture. However, it ispreferred to use between 0.5 and 1.5 mole equivalents of scavenger permole of free formaldehyde present at the end of the resole reaction. Theunique stability of the two-stage formaldehyde - phenol reaction productpermits this unusually wide choice of scavenger and scavengerconcentration and allows resoles to be produced with free formaldehydeand free phenol contents of 1 weight percent and less.

The emulsifiable systems are prepared by addition of between 1 and 12parts by weight of emulsifier per 88 to 99 parts of resole. Anemulsifier which will contribute to formation of stable phenolic resinemulsions upon the dilution of the emulsifiable system with water isused. The preferred emulsifiers are proteinaceous compounds which aresoluble in aqueous media at a pH of from 6 to 8.5. Aqueous solutions ofthe proteinaceous compounds are prepared in the presence of sufficientalkali metal hydroxide, ammonium hydroxide, or organic amines such astriethylamines to provide a pH in the range of 7 to 10. The viscosity ofthe protein solution can be controlled by the addition of amides orureas. Suitable proteinaceous compounds include casein and soya proteinof molecular weights ranging from 100,000 to 400,000. For example withcasein, and aqueous solution is prepared by dissolving urea in water andcasein is added to form a slurry. After some 30 to 60 minutes, aqueoussodium hydroxide is added and mixing is continued until a solution hasformed. The solution is then added to the aqueous resole. Otheremulsifier systems which may be conveniently used are combinations ofgum arabic and polysaccharides consisting essentially of mannose andgalactose units or consisting essentially of D-mannuronic andL-guluronic acid units wherein the ratio of the gum arabic to the otherpolysaccharides is about 0.5 to about 20:1.

The clear, one phase, homogeneous, emulsifiable resins of this inventionmay be easily converted to resin in water emulsions by the simpleaddition of water with sufficient agitation to permit effective blendingof the water. This can normally be accomplished with the use ofconventional propellor, blade or turbine agitators. Depending upon thedegree of dilutibility of the emulsifiable resin, i.e., degree ofadvancement, the formation of phenolic resole emulsion may be firstcharacterized by a slight lowering of viscosity as the initial wateradded dissolves, followed by a rapid increase in viscosity with theformation of a water-in-oil emulsion and a peak viscosity at the pointat which the system inverts to a resin in water emulsion. Such is thecase with relatively high degree of advancement of emulsifiable resinsystems having a relatively low degree of water dilutibility, e.g. 20percent. Alternately, with lower advanced phenolic resole emulsifiableresins, emulsification may be accompanied by no noticeable increase inviscosity and result directly in a resin in water emulsion.

In either case, the resin in water emulsions formed are characterized byexcellent stability with regard to sedimentation and shear. Particlesize is also extremely small, in all cases being below 2μ and normallyaveraging 0.02-0.8μ.

The emulsified resin systems of this invention are useful as binders forthermal insulation and in the impregnation of cellulosic sheet members.Typical resin solids contents of the emulsified phenolic for cellulosicsheet impregnation range from about 5 percent up to 45 weight percentresin solids. Commonly, the quantity of resin falls in the range of fromabout 8 to 25 percent solids. Impregnation is accomplished by anyconvenient means, whereupon the substrate material is dried to lowervolatiles content and then is heated to advance the resin to a desireddegree. Typical quantities of resin in a treated sheet range from about10 to 40 weight percent with amounts ranging from about 15 to 30 weightpercent being particularly common. The resin treated sheet members areemployed in the manufacture of automotive oil filters, air filters andfuel filters, the individual sheets being folded, convoluted, etc. andthen packaged in an appropriate filter cartridge, as all of thoseskilled in the art fully appreciate.

The stable single phase aqueous phenol formaldehyde resins of thisinvention are particularly useful in applications which require lowpollution potential on application. Because of the low levels ofresidual phenol and formaldehyde possible by this invention and theability to use a variety of formaldehyde scavengers with the resin tofurther lower the formaldehyde content, undersirable volatiles generatedby drying and curing the resole emulsions are significantly reduced. Theaqueous resole emulsions also possess very little of the strong odor ofphenol and formaldehyde and this lack of odor is readily apparent whenthe resole is applied from open dip tanks, or coaters onto substrateswhich are passed over drying rolls, through drying ovens, or into curingpresses and ovens perhaps in poorly vented areas. Also, cured productsproduced with these resins are relatively free of residual odor causedby entrapped volatiles such as phenol, formaldehyde and their reactionproducts.

The following examples are set forth to illustrate the principles andpractices of this invention to one skilled in the art. They are notintended to be restrictive but merely to be illustrative of theinvention. Unless otherwise stated, all parts, percentages and ratiosare on a weight basis. Solids are determined by the Owens solids method.

EXAMPLE I ACID STAGE REACTION

A phenol formaldehyde acid catalyzed condensate is prepared by reacting0.28 mole of aqueous formaldehyde (50 percent) per 1 mole of phenol inthe presence of 0.004 mole of oxalic acid at atm. reflux until theformaldehyde consumption exceeds 98 percent.

BASE STAGE REACTION

The acid stage reaction product is neutralized with 0.2 moles of sodiumhydroxide and 2.26 moles of aqueous formaldehyde (50 percent) is added.A base catalyzed reaction is conducted at 65°C. in the presence of 0.15mole of calcium hydroxide until the unreacted formaldehyde content dropsto 2.3 percent. The reaction is cooled to 40°C. and 0.075 mole ofaqueous ammonia (29 percent) is added. The resin is neutralized withcarbon dioxide. The precipitated calcium carbonate is removed bycentrifuging or filtration. Five parts of a 20 percent casein proteinsolution is mixed with 100 parts of the aqueous resin to form anemulsifiable system.

Preparation of the casein protein solution is accomplished as follows:Urea (30 parts) is dissolved in water (49 parts) and casein (20 parts)is added and slurried. After 30 minutes, 29 percent ammonina (1 part) isadded and allowed to mix for 30 minutes. This solution may then be addedto the resin.

The protein containing resin forms a stable emulsion when it is dilutedwith water. The undiluted resin can be stored at 0°C. for >1 monthwithout precipitation of components or phasing. Resin properties aresummarized in Table I.

EXAMPLE II BASE STAGE REACTION

No acid stage reaction is conducted. A base catalyzed aqueous resin isprepared by reacting 2.54 mole of aqueous formaldehyde (50 percent) per1 mole of phenol in the presence of 0.02 mole of sodium hydroxide and0.15 mole of calcium hydroxide. The reaction is conducted until theunreacted formaldehyde content drops to 2.3 percent. The reaction iscooled to 50°C. and 0.075 mole of aqueous ammonia (29 percent) is added.The resin is neutralized with carbon dioxide. The precipitated calciumcarbonate is removed by centrifuging or filtration. Five parts of a 20percent casein protein solution (prepared as in Example I) is mixed with100 parts of the aqueous resin to form an emulsifiable system.

The protein containing resin will form a stable emulsion when diluted tothe point of phasing with water. However, the undiluted resin displaysvery poor storage stability at 0° to 5°C. with crystal formation beingobserved after one day. The crystal formation becomes massive after oneweek. Resin properties are listed in Table I.

EXAMPLE III ACID STAGE REACTION

A phenol-formaldehyde acid catalyzed condensate is prepared by reacting.08 mole of aqueous formaldehyde (50 percent) per 1.0 mole of phenol inthe presence of 0.004 mole equivalents of sulfamic acid at atm. refluxuntil the formaldehyde consumption exceeds 98 percent.

BASE STAGE REACTION

The acid stage reaction product is reacted in the presence of 0.10equivalents of calcium hydroxide and 2.90 mole of formaldehyde (50percent aqueous) at 70°C. until the unreacted formaldehyde drops to 6.8percent. The reaction is cooled to 50°C. and 0.26 mole of aqueousammonia (29 percent) and 0.55 mole of urea are added as formaldehydescavengers. The resin is neutralized to a pH of 7.2 with acid. Theneutralized product (100 parts) is blended with 5 parts of premixed soyaprotein solution.

Premixing of the soya protein is identical to the casein proteingprocedure given in Example I.

The resulting resin forms a stable emulsion when diluted with water. Theundiluted resin can be stored at 0°C. for >1 month without precipitationof components or phasing. Resin properties are summarized in Table I.

EXAMPLE IV BASE STAGE REACTION

No acid stage reaction is conducted. A base catalyzed aqueous resin isprepared by reacting 2.98 mole of aqueous formaldehyde (50 percent) per1 mole of phenol in the presence of 0.1 mole equivalents of calciumhydroxide at 70°C. reflux until the unreacted formaldehyde content dropsto 6.7 percent. The reaction is cooled to 50°C. and 0.26 mole of aqueousammonia (29 percent) and 0.55 mole of urea are added as formaldehydescavengers. The resin is neutralized to a pH of 7.5 with acid and isthen blended with soya protein as indicated in Example III.

The resulting resin forms a stable emulsion when diluted with water. Theundiluted resin is unstable to storage at 0°C. with crystalline depositsforming within one week. Resin properties are summarized in Table I.

EXAMPLE V

Example I is repeated using 0.28 mole of aqueous formaldehyde (50percent) per 1.0 mole of phenol during the acid stage. The basecatalyzed stage using 0.14 mole of calcium hydroxide and 2.07 mole ofadditional formaldehyde is reacted to a 1.8 percent formaldehyde endpoint at 60°C. The reaction is cooled to 50°C. and 0.064 mole of aqueousammonia (29 percent) and 0.16 mole of urea are added. The product isneutralized to a pH of 7.9 and then blended with soya protein asindicated in Example III.

The resulting resin forms a stable emulsion when diluted with water. Theundiluted resin can be stored at 0°C. for >1 month without precipitationof components or phasing. Resin properties are summarized in Table I.

EXAMPLE VI

Example I is repeated using 0.16 mole of aqueous formaldehyde (50percent) per mole of phenol in the presence of 0.004 mole of sulfamicacid during the acid stage. The base catalyzed stage using 0.14 mole ofcalcium hydroxide and 2.38 mole of additional formaldehyde is reacted to2.2 percent formaldehyde end point at 65°C. The reaction is cooled to55°C. for one half hour. Then 0.064 mole of aqueous ammonia (29 percent)is added. The product is neutralized to a pH of 8.0 and then blendedwith soya protein as indicated in Example III.

The resulting resin forms a stable emulsion when diluted with water. Theundiluted resin can be stored at 0°C. for one month without precipiationof components or phasing. Resin properties are summarized in Table 2.

The properties of the emulsifiable resole system are tabulated in TableI. The properties are measured directly on neutralized resin unlessindicated otherwise. The values for the mole ratio of formaldehydecombined with phenol (combined F/P), degree of polymerization and numberaverage molecular weight (M_(n)) of the resole components are determinedby nuclear magnetic resonance procedures as described in J. Polym. Sci.A-1,3, 1079 (1965). The stability of the aqueous emulsifiable resoles ismeasured on refrigerated samples at 0° to 5°C. and indicates the time indays to appearance of a crystalline phase or insolubles in the solution.The formaldehyde content of the reaction mixtures and final products isdetermined by the hydroxylamine hydrochloride test.

                                      TABLE I                                     __________________________________________________________________________    EMULSIFIABLE RESOLES: COMPARISON OF PROPERTIES                                                 I     II    III    IV     V      VI                          __________________________________________________________________________    Reactants, moles per mole                                                     of phenol                                                                     Total Formaldehyde                                                                             2.54  2.54  2.98   2.98   2.35   2.54                        Acid Stage Formaldehyde                                                                        0.28  0     0.08   0      0.28   0.16                        Formaldehyde Scavenger                                                         Ammonia         0.075 0.075 0.26   0.26   0.064  0.064                        Co-Reactant     0     0     0.55(1)                                                                              0.55(1)                                                                              0.16(1)                                                                              0.15(2)                     Emulsifiable Resin Properties                                                 pH               7.7   7.7   7.3    7.5    7.9    8.0                         Owens Solids     51.1  51.4  50.9   51.2   54.1   51.9                        Brookfield Visc., cps                                                                          38    25    24     21     46     33                          Water Tolerance  Emulsifies                                                                          Emulsifies                                                                          Emulsifies                                                                           Emulsifies                                                                           Emulsifies                                                                           Emulsifies                  Free Formaldehyde, %                                                                           0.8   0.8   0.3    0.5    0.3    0.5                         Free Phenol, %   0.68  1.40  0.75   0.66   1.13   0.94                        Combined F/P     2.30  2.38  2.28   2.29   2.10   2.30                        Mn               279   204   252    249    282    273                         Degree of Polymeriza-                                                         tion             1.80  1.26  1.63   1.59   1.90   1.76                        Stability, Days at 0-5°C.                                                               >1 month                                                                            ˜1 day                                                                        >1 month                                                                             <1 week                                                                              >1 month                                                                             >1 month                    __________________________________________________________________________     Co-reactant                                                                   (1)urea                                                                       (2)melamine                                                              

The data of Table I show the stability of the aqueous emulsifiableresoles of Examples I, III, V and VI which comprise resoles prepared bythe two-stage reaction process of the present invention. In comparison,Examples II and IV which comprise conventional resole compositionssimilar in molar ratios to the resoles of the present invention andpossessing similar low values for free formaldehyde and free phenol,show phase separation within a short time after preparation. Theseemulsifiable systems containing conventional resoles are thereforeunsuitable for shipping and storage because the crystalline componentstend to block lines and filters, and they are unsuitable in applicationbecause the crystalline components impair uniformity of impregnation.When these emulsifiable systems are heated to redissolve the crystallinephase, the resole components increase in molecular weight and becometackier so that application to substrates is impaired.

From the foregoing, it is obvious that many variations are possible inthe practice of the invention, without departing from the spirit andscope thereof.

What is claimed is:

1. An aqueous solution of an emulsifiable resole wherein the solutionhas a pH in the range 6 to 8.5 and contains less than 2 percent of freephenol, less than 2 percent of free formaldehyde and between about 1 andabout 12 percent of an emulsifier based on the weight of the resole andwherein the resole has a number average molecular weight of less than300, a water tolerance between about 100 and 800 percent, a combinedformaldehyde to phenol molar ratio in the range of 2.0:1 to 2.9:1, andcontains sufficient methylolated 2,2'- and2,4'-dihydroxydiphenylmethanes to inhibit crystallization of the resolesolution and wherein the emulsifier is selected to provide a stableemulsion of the resole when water in excess of the water tolerance isadded to the solution.
 2. The aqueous solution of claim 1 wherein theresole has a number average molecular weight in the range of 180 to 300and comprises between 5 and 90 weight percent of methylolateddihydroxydiphenylmethanes of which between 5 and 50 weight percent aremethylolated 2,2'- and 2,4'-dihydroxydiphenylmethanes.
 3. The aqueoussolution of claim 1 wherein the resole comprises less than 1 weightpercent free phenol and less than 1 weight percent free formaldehyde. 4.The aqueous solution of claim 1 wherein reduction of formaldehyde toless than 2 percent based on the weight of the resole is achieved with aformaldehyde scavenger wherein said scavenger is present in amounts upto 0.6 mole per mole of phenol in the original reaction mixture.
 5. Theaqueous solution of claim 4 wherein the scavenger is a soluble nitrogenorganic compound of molecular weight less than 300, containing at leastone N--H group per molecule which is reactive with formaldehyde.
 6. Theaqueous solution of claim 1 wherein the emulsifier is a proteinaceouscompound soluble in aqueous media at a pH of 6 to 8.5.
 7. The aqueoussolution of claim 6 wherein the proteinaceous compound is casein.
 8. Theaqueous solution of claim 6 wherein the proteinaceous compound is soyaprotein.
 9. An aqueous emulsion obtained by adding water in excess ofthe water tolerance to the aqueous solution of claim
 1. 10. A process ofpreparing an aqueous storage stable emulsifiable resole solution whichcomprises:a. reacting 1.0 mole phenol with from 0.05 to 0.30 molesformaldehyde under conditions for formation of novolac resin, b. addingfrom 1.75 to 3.5 moles formaldehyde and reacting under basic conditionsto produce a resole of molecular weight less than 300, and containingless than 2 weight percent free phenol, c. adjusting the pH of theaqueous resole to between about 6 and 8.5, and d. adding between 1 and12 percent of an emulsifier based on the weight of the resole, selectedto provide a stable emulsion of the resole when water in excess of thewater tolerance is added to the resole solution.
 11. The process ofclaim 10 wherein the pH is adjusted to between about 7 and
 8. 12. Theprocess of claim 10 wherein the novolac reaction stage is carried out inthe presence of 0.001 to 0.02 mole equivalents of a soluble acidcatalyst per mole of phenol at a temperature in the range of 60° -200°C. and wherein the acid has a pK of less than
 5. 13. The process ofclaim 12 wherein the catalyst has a pK of less than 2 and wherein thetemperature is in the range of 100° to 120°C.
 14. The process of claim10 wherein the resole reaction stage is carried out in the presence of asoluble basic catalyst of pK greater than about 9.0 at a temperature inthe range of 40° to 80°C., the concentration of base being between about0.05 to 0.3 mole equivalent per mole of phenol in excess of the amountrequired to neutralize the acid of the novolac reaction stage.
 15. Theprocess of claim 14 wherein the temperature is in the range of 50° -70°C. and the base is selected from the group consisting of alkali metalhydroxides, alkali metal carbonates, alkaline earth hydroxides, ammoniaand amines of molecular weight less than
 300. 16. The process of claim10 wherein a soluble nitrogen containing organic compound of molecularweight less than 300 containing at least one N--H group reactive withformaldehyde is added as a formaldehyde scavenger to the resole afterthe free phenol content has dropped to less than 2 weight percent of theresole and is reacted with the free formaldehyde to reduce theformaldehyde concentration to less than 2 weight percent of the resolewherein said scavenger is present in amounts up to 0.6 mole per mole ofphenol in the original reaction mixture.
 17. The process of claim 16wherein the formaldehyde scavenging reaction is carried out at atemperature in the range of 20° - 60°C. and the scavenger is selectedfrom the group consisting of ammonia, primary and secondary amines,urea, substituted ureas, primary amides, dicyandiamide, guanidines andaminotriazines.
 18. The process of claim 10 wherein the emulsifier is aproteinaceous compound soluble in aqueous media at a pH in the range of6 to 8.5.
 19. The process of claim 18 wherein the proteinaceous compoundis selected from the group consisting of casein and soya protein.